The present invention relates to a starting system adapted for use with a car engine, especially a gasoline engine of an automobile.
For smoother starting of a gasoline engine at a low temperature, a richer air-fuel mixture should be supplied to combustion chambers of the engine. Therefore, a carburetor for supplying the air-fuel mixture to the combustion chambers is provided with a choke valve in the vicinity of its intake portion. The choke valve serves to constrict an air intake passage in the carburetor, thereby reducing the quantity of air fed into the combustion chambers of the engine. Thus, a rich air-fuel mixture can be fed into the combustion chambers by operating the choke valve.
The choke valve may be switched by manual or automatic remote control. When remotely operating the valve, however, it must be mechanically coupled to a manual control knob or an actuator by means of a linkage or the like. Accordingly, the mechanical arrangement surrounding the carburetor is complicated.
Instead of using the choke valve to throttle the flow of air in the intake passage, an electrically-operated fuel resupply pump may be used to supply auxiliary fuel to the intake passage. In this case, the amount of fuel supplied to the intake passage is increased by the pump. Thus, as in the aforesaid case, a rich air-fuel mixture can be fed into the combustion chambers of the engine, improving the starting performance of the engine.
For the fuel resupply pump, a plunger-type electromagnetic pump may be used which comprises a plunger for pumping action and a solenoid for reciprocating the plunger in cooperation with a return spring. The quantity of auxiliary fuel delivered from this pump per unit time may easily be changed by varying the period of a pulse voltage applied to the solenoid. Thus, the starting performance of the engine is improved, and a necessary quantity of fuel can be supplied to the intake passage of the carburetor in accordance with the operating state of the engine.
According to this arrangement, a predetermined quantity of auxiliary fuel can be accurately delivered from the fuel resupply pump when the engine is in any other operating state than a starting mode. When the engine is in the starting mode or cranking state such that it is externally rotated by a starting motor, however, the pump sometimes cannot supply the intake passage of the carburetor with the necessary quantity of auxiliary fuel for the cranking state. This is because if the starting motor is actuated when the battery voltage of the engine is not high enough, the battery voltage is greatly lowered to cause a substantial drop of the pulse voltage applied to the solenoid of the fuel resupply pump. More specifically, if the pulse voltage, even with a constant period, is lowered, the electromagnetic force of attraction of the plunger produced by the solenoid is reduced. As a result, the action of the plunger against the urging force of the return spring is subject to a response time lag, so that the plunger cannot enjoy a satisfactory stroke.
Thus, in some cases, the fuel resupply pump cannot provide the necessary quantity of fuel for the starting of the engine which may possibly cause a drop of the pulse voltage supplied to the solenoid. In other words, the engine cannot maintain a reliable starting performance.